356 HEAVY OILS (LUBRICATING OILS) With a pale oil, 10 grams are dissolved in about 150 c.c. of a perfectly neutral mixture of ether (4 parts) and alcohol (i part) and the solution titrated with decinormal alcoholic sodium hydroxide in presence of phenolph- thalein. If the colour of the oil is too intense to admit of observation of the colour change of phenolphthalein, 10 grams of it are shaken with 100 c.c. of absolute alcohol and 50 c.c. of the separated alcoholic layer titrated with decinormal alcoholic caustic soda in presence of phenolphthalein.1 The acidity is expressed as sulphuric anhydride or oleic acid, or as the number of milligrams of potassium hydroxide necessary to neutralise i gram of the oil, the last being termed the acidity number of the oil; i% S03 = 7-05% oleic acid = acidity number of 14. 3. Alkalinity.—This is detected by adding phenolphthalein to another aliquot part of the water with which the oil was shaken in the determina- tion of the mineral acids ; with free alkali a red coloration is obtained. It must be borne in mind that, if the oil in question contains alkali soaps, the alkalinity found may be due to partial decomposition (hydrolysis) of the soap by water. 4. Determination of the Solid Paraffin and Asphalt.—As in crude petroleum (q.v., Chemical Tests, 4 and 5). 5. Detection of Oils, Fats and Waxes.—(i) QUALITATIVE. 5 c.c. of the mineral oil are heated for about 15 minutes in a test-tube with a stick of caustic soda weighing about 4 grams, either over a naked flame or, better, in a paraffin bath at 200-210°. If fatty substances are present, even only to the extent of 1-2%, the whole mass becomes solid and gelatinous on cooling. (2) QUANTITATIVE. If the qualitative test gives a positive result, the quantitative estimation may be carried out as follows : (a) By the saponification number determined as indicated for fatty substances ; about 5 grams of substance are used and, besides alcoholic potash, an equal quantity of benzene is added, the heating in a reflux appara- tus being continued for about an hour. The saponification number thus obtained is divided by 1-85, the result being the percentage of fatty sub- stances calculated from the mean value of their saponification number. In presence of wool fat or waxes—which are usually detectable by the odour and consistency—the results obtained are inaccurate, since these substances have saponification numbers different from those of fatty substances. (6) By direct weighing, according to the directions given by Armani and Roda.no2: 5 grams of the oil are saponified in a flask with alcoholic potash solution (12 grams of caustic potash in 100 of alcohol), the flask being immersed in a bath of boiling water. As reflux apparatus, a simple funnel is placed in the mouth of the flask, so that a large part of the alcohol is 1 According to H. Loebell (Chem. Zeit., 1911, 35, p. 276), the acidity is determined in 10 c.c. of the oil, using an alcohol-benzene mixture (i : 2) as solvent, alkali blue as indicator and decinormal alcoholic caustic soda as standard solution. 2 Industria saponiera, Milan, 1912, p. 169; Ann. Lab. chim. oentrale Gabelle, Vol. VII, p. 278.water.l2, 22-5.